砂土中海上风机筒型基础沉放过程筒—土作用研究
发布时间：2018-12-28 16:17
【摘要】：筒型基础是一种比较常见的海上平台基础形式，具有节约成本和环保等优点，近年来开始被用作海上风机结构基础。沉放安装是筒型基础关键施工过程，也是其实现工程应用的前提，而目前其沉放过程还存在诸多问题。 针对海上风机筒型基础沉放过程，结合现有研究和工程中存在的问题，通过模型试验和数值模拟方法，开展了砂土中筒型基础沉放过程筒—土作用研究，揭示了筒型基础静压沉放过程中的挤土效应、负压沉放过程中的减阻效应、沉放阻力与渗流特性以及复合筒型基础的负压沉放与调平特性，并在此基础上改进了已有沉放阻力和沉放所需负压的计算方法。本文主要研究工作和创新成果如下： （1）针对长径比（L/D）为1.0的传统筒型基础结构和长径比为0.33的宽浅式筒型基础结构，分别开展了筒型基础静压沉放试验，发现筒壁下沉过程中存在明显的挤土效应，使得周围土体应力水平大大提高；L/D=1.0基础还存在土塞效应，内侧土压力远大于外侧；端阻力在总沉放阻力中起主要作用；已有阻力计算方法不能准确预测筒型基础静压贯入阻力。在对试验数据分析的基础上，提出了一种能更准确地预测静压沉放阻力的、基于静力触探试验和静压管桩理论的计算方法。 （2）针对目前负压沉放存在的问题，利用上述两个筒型基础开展了负压沉放试验，揭示了负压下沉过程中筒壁内、外侧摩擦力和端部阻力的变化规律，发现负压下沉时内侧摩阻力与端阻力大大减小，而外侧摩阻力几乎不变；现有临界负压是过于保守的，即使施加负压超过临界负压值也不会发生渗透破坏。并揭示了沉放减阻效果与施加负压之间的关系，改进了现有沉放所需负压计算方法。 （3）针对海上风机复合筒型基础这一新型筒型基础结构，通过数值模拟和模型试验方法，开展了负压沉放与调平研究，揭示了其沉放和调平过程中负压与渗流特性，以渗流出口水力梯度为控制条件，建立了复合筒型基础沉放和调平临界负压计算公式，发现复合筒型基础沉放所需负压略小于未分舱基础情况；当复合式筒型基础在沉放过程中发生倾斜时，可通过抽吸升高舱体气体实现快速调平，且施加调平负压小于临界负压，，在多个舱体内施加负压调平可以降低调平负压值。
[Abstract]:Cylindrical foundation is a common offshore platform foundation with the advantages of cost saving and environmental protection. It has been used as the structural foundation of offshore fan in recent years. Sinking installation is the key construction process of cylindrical foundation, and is also the premise of its engineering application. However, there are still many problems in the sinking and laying process. In view of the sinking process of offshore fan tube foundation, combined with the existing research and engineering problems, through the model test and numerical simulation method, the research on the tube-soil interaction during the sinking process of the tube foundation in sand is carried out. The soil squeezing effect, drag reducing effect, sinking resistance and percolation characteristics and the negative pressure sinking and leveling characteristics of the cylindrical foundation during the static pressure sinking and laying are revealed, and the negative pressure sinking and leveling characteristics of the composite cylinder foundation are also revealed. On this basis, the existing calculation method of sinking resistance and negative pressure is improved. The main achievements of this paper are as follows: (1) for the traditional cylindrical foundation with a aspect ratio of 1.0 and the wide-shallow cylindrical foundation with a aspect ratio of 0.33, The static pressure sinking test of cylindrical foundation was carried out, and it was found that there was obvious soil squeezing effect in the process of cylinder wall sinking, which greatly improved the stress level of surrounding soil. There is also soil plug effect in L/D=1.0 foundation, the inner earth pressure is much larger than the outside, the end resistance plays a major role in the total sinking resistance, and the existing resistance calculation method can not accurately predict the static pressure penetration resistance of the cylindrical foundation. Based on the analysis of test data, a calculation method based on static penetration test and static pressure pipe pile theory is proposed, which can predict the static pressure sinking resistance more accurately. (2) in view of the problems existing in the negative pressure sinking at present, the negative pressure sinking test is carried out by using the above two cylinder foundations, which reveals the variation law of the friction force and the end resistance in the inner and outer side of the cylinder wall during the negative pressure sinking. It is found that the inner friction and the end resistance are greatly reduced while the lateral friction is almost unchanged when the negative pressure is sinking. The existing critical negative pressure is too conservative, even if the negative pressure is applied above the critical negative pressure value, there will not be osmotic damage. The relationship between the effect of drag-reduction and the application of negative pressure is revealed, and the existing calculation method of negative pressure is improved. (3) in view of the new type of tubular foundation of offshore fan composite cylinder foundation, through numerical simulation and model test method, the research of negative pressure sinking and leveling is carried out, and the characteristics of negative pressure and seepage in the process of sinking and leveling are revealed. Taking the hydraulic gradient of seepage outlet as the control condition, the formulas of settling and leveling critical negative pressure of composite cylindrical foundation are established. It is found that the negative pressure required for sinking of composite cylindrical foundation is slightly smaller than that of non-subdivision foundation. When the compound cylinder foundation tilts in the process of sinking, it can be quickly leveled by pumping and raising the cabin gas, and the leveling negative pressure is less than the critical negative pressure, and the negative pressure adjustment value can be reduced by applying the negative pressure adjustment in multiple tanks.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU476
本文编号：2394166
[Abstract]:Cylindrical foundation is a common offshore platform foundation with the advantages of cost saving and environmental protection. It has been used as the structural foundation of offshore fan in recent years. Sinking installation is the key construction process of cylindrical foundation, and is also the premise of its engineering application. However, there are still many problems in the sinking and laying process. In view of the sinking process of offshore fan tube foundation, combined with the existing research and engineering problems, through the model test and numerical simulation method, the research on the tube-soil interaction during the sinking process of the tube foundation in sand is carried out. The soil squeezing effect, drag reducing effect, sinking resistance and percolation characteristics and the negative pressure sinking and leveling characteristics of the cylindrical foundation during the static pressure sinking and laying are revealed, and the negative pressure sinking and leveling characteristics of the composite cylinder foundation are also revealed. On this basis, the existing calculation method of sinking resistance and negative pressure is improved. The main achievements of this paper are as follows: (1) for the traditional cylindrical foundation with a aspect ratio of 1.0 and the wide-shallow cylindrical foundation with a aspect ratio of 0.33, The static pressure sinking test of cylindrical foundation was carried out, and it was found that there was obvious soil squeezing effect in the process of cylinder wall sinking, which greatly improved the stress level of surrounding soil. There is also soil plug effect in L/D=1.0 foundation, the inner earth pressure is much larger than the outside, the end resistance plays a major role in the total sinking resistance, and the existing resistance calculation method can not accurately predict the static pressure penetration resistance of the cylindrical foundation. Based on the analysis of test data, a calculation method based on static penetration test and static pressure pipe pile theory is proposed, which can predict the static pressure sinking resistance more accurately. (2) in view of the problems existing in the negative pressure sinking at present, the negative pressure sinking test is carried out by using the above two cylinder foundations, which reveals the variation law of the friction force and the end resistance in the inner and outer side of the cylinder wall during the negative pressure sinking. It is found that the inner friction and the end resistance are greatly reduced while the lateral friction is almost unchanged when the negative pressure is sinking. The existing critical negative pressure is too conservative, even if the negative pressure is applied above the critical negative pressure value, there will not be osmotic damage. The relationship between the effect of drag-reduction and the application of negative pressure is revealed, and the existing calculation method of negative pressure is improved. (3) in view of the new type of tubular foundation of offshore fan composite cylinder foundation, through numerical simulation and model test method, the research of negative pressure sinking and leveling is carried out, and the characteristics of negative pressure and seepage in the process of sinking and leveling are revealed. Taking the hydraulic gradient of seepage outlet as the control condition, the formulas of settling and leveling critical negative pressure of composite cylindrical foundation are established. It is found that the negative pressure required for sinking of composite cylindrical foundation is slightly smaller than that of non-subdivision foundation. When the compound cylinder foundation tilts in the process of sinking, it can be quickly leveled by pumping and raising the cabin gas, and the leveling negative pressure is less than the critical negative pressure, and the negative pressure adjustment value can be reduced by applying the negative pressure adjustment in multiple tanks.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU476
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